A gas circuit breaker is installed in an electrical substation or an electrical generating station or the like and it interrupts a current by blowing gas between electrodes which are driven by an actuator in case of a system accident such as an earth fault and a short circuit and works to prevent equipment such as transformers from being damaged. If the gas circuit breaker fails to interrupt a current because it is faulty, the extent of the accident expands and a significant trouble occurs; so, it requires high reliability. A major cause of making a gas circuit breaker faulty is a mechanism system trouble, it is thought that monitoring the operating characteristics of a gas circuit breaker enables it to obviate most of accidents.
In Patent Literature 1 and Patent Literature 2, for monitoring the operating characteristics of a switch to open and close a main circuit of electric power equipment, the following method is taken: when a command is given to monitor the operating characteristics of the switch, a judgment is made as to whether the operating characteristics of the switch are right or wrong by monitoring a period after the command is given until the switch starts to operate and a subsequent period until the operation finishes, based on an excitation current flowing through a closing coil or a tripping coil and detection signals indicating positions of a movable contactor.